EDM apparatuses utilizing a wire electrode are commonly presently used in making precise cuts on various electrically conductive materials, such as metals, and cutting the metal or workpiece into a given desired configuration or shape. In general, the wire electrode is caused to travel between two turning spools and a pair of wire guides wherethrough the wire travels are used to accurately situate or guide the wire at the proper location and angle with respect to the workpiece being cut. The wire and workpiece are placed at different electrical potentials, and a controlled electric spark traveling between the wire and workpiece causes the workpiece to be eroded and cut in the desired shape or configuration.
The position of the wire guides is controlled by mounting the wire guides to a respective upper and lower arm and selectively moving the arms and, thus, the wire guides, in a predetermined desired direction. The wire guides are also quite often part of an overall guide assembly adapted for flushing the wire guide with EDM electrolytes or dielectrics such as deionized water, petroleum based liquids, water with additives and other liquids, hereinafter collectively referred to as EDM liquids, for cooling the guide assembly and flushing the workpiece.
The older wire guides as, for example, is disclosed in Haug et al., U.S. Pat. No. 4,250,371 utilized grooved guides for positioning the wire electrode with respect to the workpiece. Further, the grooved guide was made of a non-conductive material, such as sapphire. A disadvantage with the grooved guides is that they are, in essence, unidirectional.
Other wire electrode guides utilize a hole or bore slightly larger in diameter than the wire electrode for guiding the wire and are, thus, multidirectional. An example of one such wire guide is disclosed in Ichikawa, U.S. Pat. No. 4,613,740. The wear resistance of the multidirectional wire guides was increased by employing a diamond guide member with a cylindrical hole and mounted in a sintered metal. Furthermore, a non-conductive cap, as disclosed in Ichikawa, U.S. Pat. No. 4,613,740 was employed at the tip of the guide and facing the workpiece so as to prevent electroerosion thereat to the wire guide.
The prior multidirectional wire guides, however, have substantial shortcomings and drawbacks. Most importantly, it has been found that over a generally short period of time, the mount around the diamond guide member deteriorates and/or the guide member becomes loose or breaks away from its mount thereby rendering the guide incapable of accurate placement or guidance of the wire electrode and, therefore, also useless. The deterioration of the mount may also create ledges or rough areas, thus, making automatic threading or manual threading difficult or time-consuming because the wire becomes caught on the formed ledges or rough areas. Although the diamond guide member is wear-resistant with regard to the friction of the wire electrode in the diamond guide hole, the life span of the guide is substantially decreased in view of the diamond guide member becoming loose or breaking away from its mount. Furthermore, wire guides employing non-conductive caps are also subject to this problem and are more difficult, time-consuming, and costly to manufacture.
Accordingly, a need exists for a multidirectional electrode wire guide that is less expensive to manufacture, is substantially wear-resistant and long-lasting and, further, wherein the mount is not deteriorated and the guide member is not demounted or dislodged from its mount during use.